Portable door knob alarm



FIG. 1 is a perspective view of a portable door knob alarm showing my new design, with the broken lines showing for illustrative purposes only and forming no part of the claimed design;

FIG. 2 is a front view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a back view thereof;

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a top plan view thereof. 

The ornamental design for a portable door knob alarm, as shown and described. 